This invention relates generally to the field of metallurgical refining in a shaft furnace. More particularly, this invention relates to a new and improved device for removing tuyere stocks from a shaft furnace. The tuyere stock removal device of the present invention is particularly well suited to be used in conjunction with those types of blast furnaces having a hot air, closed circuit pipe line running a circular course around the bosh, the pipe line being concentric to the vertical axis of the furnace. The novel tuyere stock removal device is suspended by means of rollers which are attached to rails, and the device forms an integrated mechanical unit with the hot air, closed circuit pipe line.
As is well known to those skilled in the art, the hearth of a conventional blast furnace is supplied with hot air, which may be enriched with oxygen, via a plurality of tuyeres mounted in the wall of the blast furnace. The hot air is supplied by air heaters which feed a closed circuit pipe line surrounding the blast furnace. Each individual tuyere is then fed from the pipe line via tuyere stocks. These tuyere stocks consist, in part, of a down pipe which slants downwardly from the closed circuit pipe line, a pipe vent is attached to the down pipe, followed by a blast nozzle which forms a horizontal connection between the pipe vent and the tuyere.. The down pipe is usually provided with equipment for compensating any thermal expansion.
The tuyeres extend into the blast furnace and are thereby exposed to a considerable amount of mechanical and thermal stresses and resulting wear. Accordingly, the tuyeres have to replaced relatively frequently. This replacement of the tuyeres, i.e., the dismantling of a defective tuyere and the subsequent installation of a new one, necessitates the temporary removal of at least the blast nozzle and pipe bend of the tuyere stock. In turn, the supply of hot air and thus, the operation of the blast furnace must be halted during this repair operation.
When smaller blast furnaces are involved, the operation of replacing the tuyeres may be carried out manually using only a few tools. It will be understood however, that in accordance with present day requirements, smaller blast furnaces are typically no longer used. Unfortunately, in the more often utilized medium to very large blast furnaces, the equipment size and weight are so great that the tuyere replacement operation and the work associated therewith can only be performed with mechanical equipment.
A device of this type, i.e., a device for the replacement of damaged tuyeres from a blast furnace, will inevitably involve dismantling of at least a part of the tuyere stock. Accordingly, this device will hereinafter be termed a tuyere stock removal device. It will be understood by those skilled in the art that an important consideration in designing a tuyere stock removal device includes optimizing the ratio of labor costs and other expenditures to overall efficiency of blast furnace operation. This optimization will require the reduction of the idle period wherein the blast furnace is not used during the replacement operation of the tuyere.
One attempted prior art solution to the problems associated with the design of an efficient tuyere stock removal device is described in German Patent Application No. 2833303, corresponding to U.S. Pat. No. 4,266,907 assigned to the assignee hereof and incorporated herein by reference. In the system discussed therein, a lifting arm attached to a floor vehicle is provided with suitably designed handling tools. These tools, which are remote controlled by the driver, effect removal of the tuyere stock. It should be understood that this floor vehicle can be have a multi-purpose construction so that during the periods of time in which the removal and replacement of the tuyere is not necessitated, the floor vehicle may be used for other purposes within the plant. As the tuyere removal operation only takes up a small fraction of the vehicles' time, the actual cost of equipment for the removal of the tuyere stock is effectively reduced to a minimum.
Unfortunately, the tuyere stock removal device as disclosed in U.S. Pat. No. 4,266,907 is only suitable for blast furnaces in which there is an uninterrupted platform or stage which surrounds the entire furnace and is disposed beneath the hot air closed circuit pipe line and the tuyere stocks. It is well known that an uninterrupted platform of this type is only found in very large modern blast furnaces. However, in other blast furnaces, because of the lack of sufficient height, the platform is interrupted above the tapholes in order to have space available for the insertion of the taphole bores and guns. Accordingly, the above discussed floor vehicles cannot remove the tuyere stocks which are situated above the gaps in the platform. As a direct consequence thereof, the tuyere stock removal device as described in U.S. Pat. No. 4,266,907 is not suitable for these types of blast furnaces, i.e., the small to medium blast furnaces.
Since, the tuyere stocks are spaced around the entire periphery of the blast furnace, and the hot air closed circuit pipe line extends around the entire periphery of the blast furnace, it has been suggested, that a tuyere stock removal device be provided which is capable of travelling along rails suspended on the pipe line. This would permit even those tuyere stocks which are located above the gaps in the platform to be serviced by the suspended tuyere stock removal device.
Suspended tuyere stock removal devices of this type have been constructed, but, unfortunately, have proven to be extremely expensive if they are to perform all of the operations to which the present invention is directed. These operations, of course, consist of dismantling the blast nozzle with its bend pipe, removal of the tuyere, and possibly dismantling the slanting down pipe. The large number of electrical and/or operating motors and their associated conductors or power supply units in these prior systems create, in part, the great expense of these devices.
Contrary to the multi-purpose floor vehicle discussed above, a suspended tuyere removal device of the type just discussed can only be used for dismantling or removing the tuyere stocks. Thus, in comparison to the floor vehicle system, the labor intensive and costly operation of installing a suspended tuyere removal device seriously detracts from the favorable features associated therewith. Moreover, since present suspended tuyere removal devices consist of a relatively complicated structure, the increase of breakdowns and problems associated with this complex structure provides a greater chance for equipment failure and therefore higher costs.
In order to construct transportable tuyere stock removal devices suspended on the hot air closed circuit pipe lines in a more practical and efficient manner, various suggestions and proposals have been made which would permit the taphole borers and/or guns to also be suspended on a tuyere stock removal device of this type. This would allow the borers and/or guns to freely move about the periphery of the furnace. This design, however, necessitates that the conventional infrastructure of the lower zone of the blast furnace be extensively altered. Accordingly, this type of suspended tuyere stock removal device cannot be used in an existing blast furnace. Moreover, the complexity of such a device would create additional cost problems.